Giardia species are a group of endoparasites that inhabit the intestinal tract and may cause clinical or subclinical infections in mammals. Detection and identification of Giardia spp. by light microscopy can be difficult or unreliable due to the sporadic shedding of cysts, inadequate number of organisms, improper specimen collection, or the interference of anti-diarrheal medication. Commercial kits utilizing ELISA or immunofluorescent antibody (FA) technologies have recently become available for the diagnosis of human giardiasis. We report here data on the efficacy of two such kits in detecting Giardia infections in hamsters and mice. Animals known to be infected with Giardia spp. as determined by fecal/cecal microscopic examinations were tested utilizing ELISA or FA serological kits. Both kits yielded positive results with hamsters but neither kit was able to detect Giardia muris in infected mice. Substitution of a specific anti-Giardia muris in the FA kit yielded positive results in mice and hamsters but was negative for Giardia lamblia from human samples. Thus, ELISA and FA assays could be a valuable adjunct to the examination for intestinal giardiasis as they can be performed quickly using non-infective formalin fixed fecal material. The detection of false negative results in the present study, however, indicates the importance of determining the exact specificity of the antisera used in the assay.